Weight-responsive chair mechanisms are used to control tilting of a seat and back assembly for the chair. In some chair constructions, the entire rearward tilting force of a seat-back assembly is controlled by a tilt control mechanism and the springs thereof which resist the entire load generated by the seat and back assembly. This load is basically generated by the body weight of the chair occupant and their movements rearwardly wherein the spring capacity of the tilt control mechanism must accommodate all of this load.
In a weight-responsive mechanism, the back is connected to a rear portion of the seat such that rearward tilting of the back essentially effects lifting of the rear of the seat wherein the weight of the occupant on the seat opposes such lifting, and therefore, serves to counterbalance much of the tilting forces being applied directly to the back. These tilting forces applied to the back are transferred to the rear of the seat by an intermediate link so that the weight of the occupant is used to resist the rearward tilt forces. While a tilt mechanism having a spring is provided, the spring capacity of this mechanism is substantially lower due to the assistance provided by the occupant's body weight in resisting tilting of the back assembly. One of the primary functions of the spring mechanism is to return the seat and back assembly to a normal upright condition when the occupant discontinues attempts to tilt the back rearwardly or when the occupant stands up from the chair.
It is an object of the invention to provide an improved weight-activated mechanism for a weight-responsive chair which provides an improved construction relative to prior art chairs of this type.
The weight-responsive chair of the invention has a back upright pivotally connected to a chair frame with a connector link that extends forwardly from the pivot point of the back and connects to a rear portion of the seat. The seat also is pivotally connected to the chair frame at the front thereof by a front pivot link wherein the combination of the front link, the chair frame, the seat and the connector link of the back upright define a four-bar linkage wherein rearward tilting of the back upright effects lifting of the rear portion of the seat. Also, the four-bar linkage preferably effects lifting of the front portion of the seat by the front link.
The improved chair of the invention further includes a tension mechanism connected between the chair frame and the rear upright to provide a relatively low level of resistance to tilting of the back upright. The tension mechanism includes a spring or biasing arrangement which serves to restore the seat and back to an upright position. The back, however, has a forwardly extending connector link projecting from the pivot mount by which the back is pivotally connected to the chair frame. This connector link is connected at its forward end to the rear portion of the seat so that rearward tilting of the upright causes the connector link to pivot upwardly and thereby lift the seat against the weight of the user. The counteracting weight of the user acting downwardly on the connector link serves to resist tilting of the interconnected back so that much of the resistance to tilting results from the weight of the user so that the chair mechanism is weight responsive.
Additionally, the seat of this chair uses a seat support frame connected to a seat panel which is pivoted at its front end to the main chair frame and at the back end to the tension mechanism. Additionally, the seat frame includes resiliently deflectable frame extensions or suspension arms which interconnect to the central portion of the rear of the seat, which cantilevered extensions allow for resilient vertical displacement of the rear portion of the seat relative to the weight-responsive mechanism. Hence, the weight-responsive mechanism does effect lifting of the rear portion of the seat while the frame extensions also permit independent resilient movement of the rear seat portion to improve comfort to the chair occupant.
Other objects and purposes of the invention, and variations thereof, will be apparent upon reading the following specification and inspecting the accompanying drawings.
Certain terminology will be used in the following description for convenience and reference only, and will not be limiting. For example, the words “upwardly”, “downwardly”, “rightwardly” and “leftwardly” will refer to directions in the drawings to which reference is made. The words “inwardly” and “outwardly” will refer to directions toward and away from, respectively, the geometric center of the arrangement and designated parts thereof. Said terminology will include the words specifically mentioned, derivatives thereof, and words of similar import.